Congenital Hand Flashcards

Question

An 18-month-old male infant with an isolated Blauth Type IV thumb (floating) is scheduled to undergo pollicization of the index finger. A photograph is shown. The index finger metacarpal head becomes which of the following structures in the pollicized thumb? A) Articular surface of the carpometacarpal (CMC) joint B) Distal articular surface of the proximal interphalangeal (PIP) joint C) Proximal articular surface of the PIP joint D) Scaphoid E) Trapezoid

Answer 1

The correct response is Option A. Thumb pollicization is a challenging yet functionally rewarding procedure. It is indicated for Blauth Type IIIB or higher thumbs. If done correctly, this technique can greatly enhance the function of the hand and provide a strong, stable thumb analog for grip and pinch. The procedure involves many stages and is technically demanding. Although beyond the scope of this description, the procedure requires shortening of the index finger metacarpal and repositioning of the metacarpal head in hyperextension against the preserved metacarpal base. Thus, the index metacarpal phalangeal joint becomes the new thumb's carpometacarpal joint, the index proximal interphalangeal joint becomes the new thumb's metacarpophalangeal joint, and the index distal interphalangeal joint becomes the new thumb's interphalangeal joint. 2020

Answer 2

The correct response is Option E. Radial longitudinal deficiency may present as an isolated condition but is often associated with an underlying syndrome. The frequency of association with a syndrome has been reported to range from 33 to 44%. Hypoplastic thumb can be present in isolation or in combination with any radial deficiency. Hypoplastic thumb is the second most frequently encountered thumb anomaly. Commonly associated syndromes with radial longitudinal deficiencies include Holt-Oram, Fanconi anemia, thrombocytopenia-absent radius, and VACTERL association (a sporadic collection of anomalies consisting of the vertebral deformity, anal atresia, cardiac anomalies, tracheoesophageal fistula, renal agenesis, and limb deformities). Holt-Oram is a syndrome passed in an autosomal dominant fashion and presents with both radial longitudinal deficiency and a cardiac anomaly, most commonly a ventricular septal defect. Both thrombocytopenia-absent radius syndrome and Fanconi anemia are transmitted in an autosomal recessive pattern. Thrombocytopenia absent radius syndrome consists of thrombocytopenia that manifests itself during infancy and can be fatal; however, it usually resolves spontaneously with age. In contrast, Fanconi anemia presents after 3 years of life, commonly around 8 to 9 years, with aplastic anemia. Historically this condition was fatal, with no method of altering the course of the anemia. Recently, however, bone marrow transplants have been performed successfully to treat the anemia and prolong the life expectancy of these patients. Lastly, the final condition seen commonly with radial longitudinal deficiency is VACTERL association. Anorectal malformations (ARM) often co-occur with upper limb anomalies, mainly of pre-axial origin. ARM patients with a major upper limb anomaly—with or without other congenital anomalies—have a twofold greater chance of a genetic disorder than have non-isolated ARM patients without upper limb anomalies. Not all upper limb anomalies in ARM patients are part of the VACTERL association. Fetal alcohol syndrome causes brain damage and growth problems, however it is not associated with thumb hypoplasia. 2020

Answer 3

The correct response is Option E. This patient has a type IV (floating thumb or pouce flottant) thumb hypoplasia best managed with thumb ablation and index finger pollicization. Thumb hypoplasia can range from a minor decrease in size to complete absence. Thumb hypoplasia may also be associated with VACTERL (vertebral abnormalities, anal atresia, cardiac abnormalities, tracheoesophageal fistula or esophageal atresia, renal agenesis and dysplasia, and limb defects), TAR syndrome, Fanconi anemia, and Holt-Oram syndrome. Given the possible association with these conditions, a workup of all potentially affected organ systems should be performed. This includes a renal ultrasound, an echocardiogram, spine x-ray studies, a complete blood count, and a chromosomal challenge test. Thumb hypoplasia may occur in an isolated fashion or in combination with radial hypoplasia, as seen in this case. The most important and difficult distinction is between types IIIa and IIIb hypoplastic thumbs. A type IIIa thumb has a stable thumb carpometacarpal (CMC) joint, whereas a type IIIb thumb does not. If the child uses the thumb for integrated pinch, the CMC joint is deemed stable. If the thumb is bypassed in favor of scissor pinch between the index and middle fingers, the CMC joint is either unstable or absent; in this case, a pollicization is recommended. A free great toe transfer is not indicated in children with thumb hypoplasia because the existing thumb CMC is not stable and pollicization would provide a better functional outcome. Flexor digitorum superficialis or abductor digiti minimi opponensplasty are both options for thumb hypoplasia reconstruction in the presence of a stable CMC joint. A first webspace deepening is typically combined with opponensplasty and metacarpophalangeal joint stabilization in children with reconstructible hypoplastic thumbs, but not for children undergoing pollicization. The patient in the image does not have a first metacarpal, and therefore cannot undergo distraction osteogenesis. 2021

Answer 4

The correct response is Option C. Amniotic band syndrome is a rare congenital anomaly with a sporadic inheritance pattern and a reported incidence that ranges between 1:1200 to 1:15,000 live births. Constriction bands may range from shallow, harmless skin depressions to deep, annular bands that may present with distal edema, neurovascular compromise, or autoamputation. There is a propensity for constriction bands to affect the more distal aspect of the upper and lower limbs (including fingers and toes) in a bilateral, asymmetric fashion. Associated conditions may include: acrosyndactyly, talipes equinovarus (clubfoot), and cleft lip/cleft palate. In this patient, constriction band excision is the most appropriate management given the increasing edema and its potential associated functional issues. Different strategies have been described for band excision and closure. Although extremity band excision was traditionally performed in two stages, one-stage resection has been performed safely by some surgeons. Limb elevation and observation is not the best treatment as it will not address the underlying cause of the worsening edema. Compression garments and collagenase injections do not have roles in the treatment of extremity constriction bands. Amputation is not the best option and would be considered only in an unsalvageable extremity. 2021

Answer 5

The correct response is Option B. Apert syndrome (acrocephalosyndactyly) is a syndrome associated with an FGFR2 gene mutation and characterized by craniosynostosis, mid-face hypoplasia, and complex syndactyly of the hands and feet. Characteristics of the Apert hand deformity include complex syndactyly of the index, middle, and ring fingers; simple syndactyly of the ring and small fingers; and a varying degree of first web space syndactyly. The Apert hand deformity has been classified into three subtypes on the basis of the increasing degree of thumb involvement and the appearance of the central digital mass. In the Apert hand deformity, the thumb may be short and radially deviated (radial clinodactyly). The other responses are not associated with Apert syndrome. Floating thumb ("pouce flottant") is a form of thumb hypoplasia (Blauth Type IV) in which there is a rudimentary digit attached to the hand only by skin and neurovascular bundle. Camptodactyly is a painless flexion contracture of the proximal interphalangeal joint most commonly involving the small finger. Macrodactyly is a rare congenital condition in which there is overgrowth of the underlying bone and soft tissue of the finger. 2021

Answer 6

The correct response is Option B. The zone of polarizing activity (ZPA) is responsible for differentiation in the anteroposterior axis. Regulation of this entity involves the sonic hedgehog and Hox b-8 proteins. Loss of the ZPA results in absence of posterior elements in the developing limb. Duplication of the ZPA leads to mirror hand and mirror foot type anomalies. The apical ectodermal ridge (AER) is the primary driver for proximal-distal limb growth. The AER is highly regulated by fibroblast growth factor, and loss of AER function leads to arrested limb development. Ventral (bone morphogenetic proteins and Engrailed-1) and dorsal (Wnt7) signaling factors are antagonistic; disruption of these signals will affect dorsal-volar patterning but also proximal-distal growth of the limb. 2022

Answer 7

The correct response is Option A. Thumb hypoplasia represents a spectrum of thumb deficiency that may range from mild generalized hypoplasia to complete absence of the thumb. The modified Blauth classification is useful not only for classifying thumb deficiency, but also for guiding management decisions. Index finger pollicization is the procedure of choice for Blauth thumb hypoplasia type IIIB, type IV, and type V. In pollicization, the index finger is transposed on its neurovascular bundles. The index metacarpal is removed from its base to the epiphysis. The new carpometacarpal joint (CMC) of the thumb is constructed by preserving the metacarpophalangeal joint of the index finger, which is fixed into hyperextension (to avoid hyperextension deformity of new CMC joint). The index metacarpal is positioned in 45 degrees of abduction and 100 to 120 degrees pronation and fixated anterior to the index metacarpal base. The index finger tendons and muscles are used to construct the functions of the new thumb. The extensor digitorum communis is sutured to the base of the new metacarpal to simulate the abductor pollicis longus. The extensor indicis proprius tendon is shortened and sutured to become the new extensor pollicis longus. Further stability is achieved by transfer of the previously mobilized index dorsal interosseous to the radial lateral band to restore abductor pollicis brevis function. The index palmar interosseous is inserted into the ulnar lateral band to construct the adductor pollicis. 2022

Answer 8

The correct response is Option C. This child has constriction ring syndrome (CRS). CRS is a rare occurrence, with the incidence reported from 1 in 1200 to 15,000 births. CRS frequently affects multiple extremities asymmetrically, with an average of three extremities involved, most often at the distal aspect of the extremity. Several characteristics are most often seen in the affected extremities including constriction rings, amputations, lymphedema distal to the ring, and acrosyndactyly (digits are fused distally, but proximally have fenestrations as fusion occurred after apoptosis in utero). Amputation or hypoplasia is usually seen distal to the ring, whereas the proximal aspect is intact and usually well-formed. CRS affecting the hands most frequently affects the index, middle, and ring fingers. Associated anomalies include syndactyly, oligodactyly, clubfoot, limb absences, body-wall defects (e.g., gastroschisis), and craniofacial anomalies, particularly facial clefts. Symbrachydactyly, which is associated with Poland syndrome, is usually present in one limb. There is true hypoplasia of the affected extremity with absent or rudimentary digits with nubbins and frequent syndactyly. Symbrachydactyly usually impacts the central digits. Poland syndrome is defined by the absence of the sternocostal head of the pectoralis major. Hematopoietic changes can be seen in radial hypoplasia. Fanconi anemia and thrombocytopenia (thrombocytopenia absent radius syndrome) are both associated with radial hypoplasia. Children with Apert syndrome (acrocephalosyndactyly) have bilateral relatively symmetric complex syndactyly, symphalangism, and craniosynostosis. 2022

Answer 9

The correct response is Option A. Blauth developed the classification for thumb hypoplasia, which consists of five grades. Manske expanded the classification system by expanding the definition of grade III into grade IIIa, which has a carpometacarpal (CMC) joint, and grade IIIb, which does not: * Blauth I thumbs have minimal shortening and narrowing, and they do not require surgical treatment. * Blauth II thumbs have narrowing of the first web space, hypoplastic thenar muscles, and an unstable metacarpophalangeal (MCP) joint. They are best treated with reconstruction. * Blauth/Manske IIIa thumbs have type II features, extrinsic tendon abnormalities, and metacarpal hypoplasia with a stable CMC joint. They do well with reconstruction. * Blauth/Manske IIIb thumbs have type IIIa features plus partial metacarpal aplasia and CMC joint instability. Because of the additional complexity of CMC joint reconstruction, thumb ablation and pollicization is generally recommended. * Blauth IV thumbs are often referred to as pouce flottant, or floating thumb. There is a neurovascular bundle coursing through the stalk of skin connecting the thumb to the hand, and these thumbs have few rudimentary bony or soft-tissue structures. These thumbs are best treated with ablation and pollicization. * Blauth V dysplasia demonstrates absence of the thumb and require pollicization. Blauth II and Blauth/Manske IIIa reconstructive options include the abductor digiti minimi (ADM or Huber) transfer and the flexor digitorum superficialis (FDS) transfer. There is no clear indication of the superiority of one over the other. The use of the ADM diminishes the power of abduction of the small finger but provides some thenar bulk. It is a better pronator of the thumb. The FDS transfer removes a flexor from the ring finger, perhaps decreasing grip strength, and fails to provide any bulk to the thenar eminence. The FDS is superior in providing palmar abduction but pronates less effectively. When additional tissue is needed to stabilize the MCP joint, the FDS can also be used to reconstruct the MCP joint as part of the transfer. Aside from pollicization, additional reconstructive options for Blauth IIIb-V dysplasia include second toe-to-hand transfer with metatarsalphalangeal (MTP) joint arthrodesis if parents and patients decide to keep a five-digit hand. Due to the level of aplasia, harvest of the MTP joint is necessary for anatomic reconstruction. The second and third toes are best used for this level of reconstruction due to the ability to harvest the MTP joint. The great toe cannot be used, as harvest of the MTP joint of the great toe will lead to gait and balance issues. Fusion of the thumb interphalangeal joint and thumb CMC ligament reconstruction and tendon interposition arthroplasty do not address any or all of the issues with the thumb dysfunction. 2022

Answer 10

The correct response is Option D. The most likely anomaly is in LIM Homeobox transcription factor 1 beta (*LMX1B*). This patient presents with nail-patella syndrome, which results in poorly developed nails and kneecaps. Nail-patella syndrome is an autosomal dominant condition associated with mutations in the *LMX1B* gene. This gene is involved in dorsal and ventral limb patterning during embryology. Limb development is controlled by signaling pathways that are located within three different signaling centers. These govern the proximal-distal, anterior-posterior, and dorsal-ventral axes of limb development. Wnt7a from the dorsal ectoderm induces the transcription factor Lmx-1b, which induces the development of dorsal structures. This transcription factor acts within the Wnt signaling pathway, which is responsible for dorsal-ventral limb development. In the ventral portion of the limb, the Engrailed-1 gene product blocks the Wnt pathway, determining the dorsal-ventral boundary. Mutation in the *FGFR2* gene can result in Apert syndrome, which is an autosomal dominant condition that presents with complex syndactyly of hands and feet. Sonic hedgehog acts within the zone of polarizing activity, which is located in the posterior margin of the limb bud and governs growth in the anterior-posterior axis. The sonic hedgehog protein signals development of the limb into radial and ulnar aspects. This is mediated by the Gli family of transcription factors, most importantly Gli3. Alterations in this pathway can result in mirror duplication. Bone morphogenetic protein (BMP) is actively involved in multiple areas of upper extremity development, but is not the key anomaly involved in this syndrome. Suppression of BMP is associated with syndactyly. 2022

Answer 11

The correct response is Option E. A Blauth Type II hypoplastic thumb deformity includes a narrow first web space, thenar muscle insufficiency, and metacarpophalangeal (MCP) joint instability. Surgical management should attempt to address all of the deficiencies at the same time. The flexor digitorum superficialis tendon of the ring finger can be used to perform an opponensplasty and a ulnar collateral ligament (UCL) reconstruction since the tendon length is typically long enough to perform both simultaneously. The narrow first web space can be addressed by various web space deepening procedures, such as a four-flap Z-plasty. In the case of multi-directional MCP joint instability or degenerative changes, arthrodesis is a reasonable option. With this patient’s unidirectional valgus instability, however, ligament reconstruction is the preferable option. Index finger pollicization is an option for Blauth Type IIIB through V thumbs, which demonstrate carpometacarpal joint instability. Therapy and serial splinting are components of postoperative management and rehabilitation, but they cannot solve the inherent UCL deficiency. Patients with Blauth Type II thumbs can sometimes also present with a clasped thumb deformity from an absent extensor pollicis brevis tendon. This can be addressed with an extensor indicis proprius tendon transfer. 2023

Answer 12

The correct response is Option E. The cause of a pediatric trigger thumb is considered congenital by some and acquired by others. Because children hold their thumb in the palm naturally, the flexed position of the interphalangeal joint is often not observed by the family until after a fall or injury that prompts a closer evaluation. The Notta nodule is often mistaken for a bony mass. Although some authors have recommended a period of splinting or observation, the majority of pediatric trigger thumbs presenting as locked in flexion require surgical release since the rate of spontaneous resolution is low. For those cases that did resolve with splinting and therapy or observation alone, it took many months to years to achieve resolution. Open surgical intervention is performed with release of the A1 pulley and sometimes a portion of the oblique pulley. The Notta nodule at the time of surgical release is shown in the photograph. Percutaneous release, although used with success in adult trigger fingers, is not appropriate for children because of the close proximity of the neurovascular structures. There is no literature addressing the treatment of pediatric trigger thumb with steroid injections; therefore, it is not recommended. Manipulation with anesthesia might be an appropriate treatment for a dislocation, which this child does not have. 2023

Answer 13

The correct response is Option D. Treatment of toe syndactyly tends to emphasize the aesthetic outcomes heavily, since there is not often a significant functional deficit that needs to be addressed. When toe syndactyly is treated with a large dorsal flap, or large dorsal Z-plasty flaps, there is typically a significant dorsal skin deficit that requires grafting. Regardless of the donor site (groin, antecubital fossa, or other site), these grafts are often a poor match, since the dorsum of the foot tends to be several shades darker than the sole of the foot, especially in patients with darker skin. The one exception might be the use of glabrous skin grafts, but although they might be a better color match, visibility of the scars may still be an issue. A couple of different techniques have been developed to decrease the visibility of the skin grafts on the dorsal aspect of the foot. These techniques use a plantar flap to create the floor of the web space and/or resurface some of the interdigital deficits, without using large dorsal web space flaps or Z-plasty flaps, so that the dorsal skin is largely undisturbed. 2023

Answer 14

The correct response is Option A. During pollicization, the extensor tendons of the index finger are used to reconstruct the extensor tendons of the reconstructed thumb. The extensor digitorum communis is shortened and attached to the proximal phalanx to act as the abductor pollicis longus. The extensor indicis proprius is shortened and repaired and acts as the extensor pollicis longus. There is no need to reconstruct both the extensor pollicis brevis and the abductor pollicis longus since they both will act as abductors of the thumb. The flexor pollicis longus is reconstructed with a flexor tendon from the index finger, specifically the flexor digitorum profundus. 2023

Answer 15

The correct response is Option A. In contrast to traumatically injured patients, children with upper limb differences use prosthetics more for social purposes than functional ones. This is because the prosthesis effectively covers up the sensation of the terminal limb and, in effect, interferes with the child’s use of the limb. Furthermore, the prosthetic socket, by blocking sensory feedback, may limit the development of functional strategies. For this reason, the rejection rate is high and there is no functional difference seen in patients who use a prosthesis versus patients who do not use one. For children and families who choose to use a prosthesis, the key timeline for fitting is to provide a passive (not activity-specific or articulating) prosthesis when the child has obtained the ability to sit balanced, usually at 9 months of age. Children fitted after 2 years of age have an even higher rate of rejection of the prosthesis. Skeletal augmentation is not required for this patient to be eligible for a prosthetic. Some children may present with nonfunctional anatomy that can be removed, although families usually choose not to. The prosthetic fitting can be performed to accommodate these parts. If the child continues to use a prosthesis, nonfunctional parts can be removed later in life to allow for more advanced prosthetic fitting. Targeted muscle reinnervation is a surgical technique used to enhance control of myoelectric prosthetics for patients after traumatic amputation. It is not an appropriate technique for a congenital limb difference. 2023

Answer 16

The correct response is Option A. Limb differences may be classified according to the Oberg-Manske-Tonkin (OMT) classification. These divide limb differences as malformations, deformations, dysplasia, and syndromes. Malformations may be of the entire limb or limited to the hand. Entire upper limb malformations may be proximodistal, radioulnar (anteroposterior), dorsoventral, or of unspecified axis. Proximodistal malformations are divided into brachymelia, symbrachydactyly spectrum, transverse deficiency, intersegmental deficiency, or whole limb duplication/triplication. Amelia is a transverse deficiency type of proximodistal entire-limb malformation. The proximodistal axis develops through the apical ectodermal ridge. Signaling in this pathway occurs primarily via fibroblast growth factor and WNT proteins. The zone of polarizing activity is responsible for anteroposterior development, and sonic hedgehog protein is secreted from the zone of polarizing activity. Dorsal and ventral ectoderms are involved in dorsal-ventral differentiation. 2023

Answer 17

The correct response is Option A. Thumb hypoplasia is classified according to degree by the modified Blauth classification as follows: * Type I – minor generalized hypoplasia * Type II – intrinsic thenar muscles hypoplasia, first web space narrowing, and ulnar collateral ligament (UCL) insufficiency * Type IIIa – similar to Type II, plus extrinsic muscle and tendon abnormalities with bone deficiency and stable trapeziometacarpal (TMC) joint * Type IIIb – same as Type IIIa, except the TMC joint is unstable or missing * Type IV – "pouce flottant" or floating thumb * Type V – absent thumb Reconstruction is planned according to the missing components. No treatment is generally needed for Type I. Type II usually requires opponensplasty with web space deepening and UCL stabilization. Type IIIa would necessitate extrinsic tendon transfer in addition to the procedures for Type II. Types IIIb, IV, and V are best treated with pollicization of the index finger after ablation of the residual thumb, if present. 2023

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Congenital Hand Flashcards

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